1. Field of the Invention
This invention relates to a chuck for holding various tools.
2. Description of the Related Art
The prior art of holding a cutting tool in a holder is that which comprises a shrink fitting method.
According to this shrink fitting method, a hole portion is expanded by heating, a proximal portion of the tool is fitted into this expanded hole, and then the hole portion is shrunk by cooling, whereby the tool is held in the hole. Thus, considerable time and labor are required for expansion and shrinkage, and the tool cannot be rapidly replaced.
The above-mentioned expansion and shrinkage method is therefore replaced by the method of holding the tool as described below. That is, as shown in FIG. 8, a hole 2 is formed inside an end surface of a tool holder 1. The hole 2 has a triangular shape having rounded corners in cross section perpendicular to an axis. This triangular shape with the rounded corners has a long radius and a short radius. The long radius extends from the center to the rounded corner located at the position where an inner periphery is trisected. The short radius extends from the center to the position where a distance between the rounded corners on the inner periphery is bisected.
To support a tool A in this holder 1, the hole portion 2 of the holder 1 is first inserted into the center of a pressurizing tool 3 as shown in FIG. 7.
In this case, as shown in FIG. 7, the rounded corners of the hole 2 are matched to pressurizing members 4 located at the positions where the pressurizing tool 3 is trisected.
Next, a handle 5 is rotated so that the pressurizing members 4 are slid toward the center as indicated by arrows of FIG. 8, while the rounded corners of the hole 2 are worked as shown in FIG. 9.
Consequently, the inner periphery of the triangular hole with the rounded corners shown in FIG. 8 is changed into the perfectly-circular hole 2 as shown in FIG. 9. The proximal portion of the tool A is inserted into this hole 2.
Then, the handle 5 is rotated, whereby while the pressurizing members 4 are slid in the directions in which the pressurizing members 4 are separated from the center (in the directions of arrows of FIG. 10), the rounded corners of the hole 2 are depressurized.
As a result, the tool A is tightly held by the portions between the rounded corners on the inner periphery of the hole 2 restored to the original shape.
The holder 1 for the tool A is pulled out from the pressurizing tool 3, and then the holder 1 is held by a chuck (not shown) rotating together with a spindle.
According to the above-described method, the tool is replaced through the following procedure. The holder is removed from the chuck, the removed holder is set in the pressurizing tool, the tool is removed from the holder by operating the pressurizing tool, the tool is held by the empty holder, and then the holder removed from the pressurizing tool is held by the chuck. However, this
Moreover, operating efficiency of a machine is reduced considerably due to the troublesome replacement.
This invention is therefore made so that the tool can be very rapidly replaced (attached and detached) with the tool attached to the spindle of a machine tool.